boards/saml21-xpro: fix typos
boards/saml21-xpro: fix typos

kYc0o/RIOT,authmillenon/RIOT,kYc0o/RIOT,ant9000/RIOT,OTAkeys/RIOT,yogo1212/RIOT,aeneby/RIOT,yogo1212/RIOT,jasonatran/RIOT,x3ro/RIOT,basilfx/RIOT,kaspar030/RIOT,mtausig/RIOT,aeneby/RIOT,kaspar030/RIOT,OlegHahm/RIOT,basilfx/RIOT,yogo1212/RIOT,OlegHahm/RIOT,mtausig/RIOT,x3ro/RIOT,toonst/RIOT,ant9000/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,toonst/RIOT,josephnoir/RIOT,kaspar030/RIOT,OTAkeys/RIOT,smlng/RIOT,authmillenon/RIOT,basilfx/RIOT,kaspar030/RIOT,aeneby/RIOT,x3ro/RIOT,kYc0o/RIOT,yogo1212/RIOT,kYc0o/RIOT,authmillenon/RIOT,toonst/RIOT,smlng/RIOT,josephnoir/RIOT,smlng/RIOT,miri64/RIOT,basilfx/RIOT,aeneby/RIOT,basilfx/RIOT,mtausig/RIOT,RIOT-OS/RIOT,smlng/RIOT,miri64/RIOT,OlegHahm/RIOT,jasonatran/RIOT,toonst/RIOT,ant9000/RIOT,OlegHahm/RIOT,mtausig/RIOT,smlng/RIOT,aeneby/RIOT,josephnoir/RIOT,authmillenon/RIOT,miri64/RIOT,jasonatran/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,OTAkeys/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,x3ro/RIOT,yogo1212/RIOT,miri64/RIOT,kYc0o/RIOT,jasonatran/RIOT,mtausig/RIOT,josephnoir/RIOT,toonst/RIOT,josephnoir/RIOT,OTAkeys/RIOT,ant9000/RIOT,OTAkeys/RIOT,yogo1212/RIOT,x3ro/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,ant9000/RIOT,miri64/RIOT